Compression release mechanism



Sept. 22, 1936. H, 5, H RCH 2,054,928

COMPRESSION RELEASE MECHANISM Filed Sept. 11,. 1933 2 Sheets-Sheet l T ORNEY? Sept; 22, 1936. H. D@ CI- lURCH 2,054,928

COMPRESSION RELEASE MECHANISM v FiledSept. 11', 1953 2 Sheets-Sheet 2 INVENTOR 1, B, ('Aw'r/z Patented Sept. 22, E936- acetate PATENT orFlcE- 2,054,028 p COMPRESSION RELEASE mzcr'mmsu Harold D. Church, Cleveland Heights, Ohio, as-

slgnor, by mesne assignments, to General Motors Corporation, Detroit, Mich, a corpora tion of Delaware Application September 11, 1933, Serial No. 688,908

Claims. (Cl. 123-182) This invention relates to internal .combustion engines, and particularly to novel means for temporarily relieving the compression in the cylinders of such an engine, thus lightening the 5 load on the engine starter. a

More specifically the engine contemplated is one having poppet valves, spring-seated and having associated actuating gear for timed ac-- tuation of the valves during running of the englue, and the compression release means contemplated is one wherein one or more valves of each cylinder of the engine may be simultaneously "cracked open, at the will of the operator.

.The object of this invention is to provide novel means for accomplishing this purpose.

The exact nature of this invention together with further objects and advantages thereof will be apparent from the following description taken in connection with the accompanying drawings,

in which Fig. l is a plan view of an-engine embodying the invention, certain parts being broken away to'show details of constructionand the valve gear cover plate being removed to show the valve gear; Fig. 2 is a typical transverse sectional elevation through pertinent parts at the head end of the same, taken as in the planes of line 2-2, iiig. l; and Fig. 3 is an enlarged detail view, partly in section, taken as in the planes of lines 33, Figs. 1 and 2.. I

With reference now to the drawinga'the engine illustrated is indicated as having but two cylinders i and 2, arranged in line, although it will be appreciated that usually a multiple of two cylinders, such as six or eight, arranged in line, would actually be employed in practice.

The engine illustrated is of the solid fuel in- 1 iection type having, for each cylinder, an injection'nozzle generally indicated at 3.

Each cylinder is shown as provided with four.

49 valves including apair of inlet valves 26 and a pair of exhaust valves d. The exhaust valves d are spring-seated, as by the compression springs 5, whereby they are yieldably maintained seated to close their ports in the cylinder head 6, such ports controlling communication between the cylinder i and the exhaust passage 1.

The pair of exhaust valves-are arranged for coincidental operation by a cradle 8 having rollers t disposed to'be effective upon the valve stems,

0 the cradle 8 including a plunger it by which its angularity is maintained, so that upon depression of the cradle 8 both valves 4 will be unseated, and upon release of the cradle 8 both valves will be reseated by their springs; this 55 being the usual functioning of the valves during the operation of the engine.

' Gear is provided for each pair of valves, in-

cluding the pairs of exhaust valves, for their timedactuation, this gear including a cam shaft 60 ii driven by suitable timing gears (not shown) in the gear case 82. The cam shaft ll extends the length of the engine and has, for each cylinder, three cams, including one 21 acting upon a roller 29 for actuating the injection device, one 28 acting upon a roller 30 for actuating the inlet 5 valves, and one, i3, for actuating the exhaust valves 4, it being understood that the cams are properly indexed on the cam shaft, and the cam shaft properly timed by its driving gearing, with relation to the crank shaft of the engine.

The cam I3 is made efiective upon the cradle 8 to control the exhaust valves 4, by a rocker M mounted upon a. rocker shaft i5 suitably mounted on the engine, between the cam shaft ii and the cradle 8.- The rocker here shown comprises a pair of members it spaced to include between them, at one end, the cradle d with which the rocker has pivotal connection by the pin ill; and carrying between them, at their opposite end, a pin it, upon which is mounted, between the 20 members it, a roller it. The roller is is arranged in the plane of the cam it, to cooperate therewith as the cam follower, whereby timed rotation of the cam shaft ill will cause timed rocking motion of the rocker it, and consequentg5 ly timed operation of the-valves 3. The cradle t, being carried by the rocker it, during motion of the rocker the rollers 9 will have slight transverse motionrelative to the valve stems. This is permitted by a suitable swinging mounting indicated generally at We at the base of the plunger it.

What has thus far been described is not new in the art and will be recognized as generally typical thereof, and it will be appreciated that all of the valves of each cylinder of the engine, including fuel injection, inlet, and exhaust valves, for each cylinder, will have timed actuation from the cam shaft it by means and in a 40 manner corresponding to that herein specifically described for the pair of exhaust valves t under consideration.

According to this invention, for each pair of exhaust valves of the engine, I provide, adjacent the corresponding rocker it, a lever 28 pivotally mounted upon the rocker shaft i5, and, located alongside the rocker preferably on the side removed from the next adjacent rocker. The lever 20 extends toward the cam follower roller E9 of the rocker and therebeyond. The pin' it upon which the cam follower roller 59 is mounted, is extended beyond the rocker it, into the plane of the lever 20, as at 2!, and the lever is provided with a slot 22 into which the pin extends. The 5 lever 20 also extends beyond the pin i8, as at 23, where it rests upon a cam 24 on a rock shaft 25.

It will be appreciated that a similar arrangement, including a lever and cooperative parts, is provided for each pair of exhaust valves, and the 99 rock shaft 25 extends lengthwise of the engine having a cam, such as at 24, for each lever 20.

The proportion and arrangement of the parts, and particularly the relation of the slot 22 and the rock shaft, is such that when the rock shaft 25 is adjusted to drop thelever 20 to its lowermost position, the cam follower roller is will rest upon its cam i 3 and theslot 22 will permit actuation of the rocker H by the cam l3; whereas if the rock shaft 25 be adjusted to the position indicated in the drawings, it will slightly raise the lever 20 so as to engage the projecting end 2| of the pin l8, and move the rocker l4 slightly clockwise to its position in Fig. 2, thereby cracking or slightly unseating the exhaust valves as shown, the roller l9 being lifted slightly from its cam i3 as indicated in Figs. 2 and 3. All of the cams 24 are similarly indexed on the rock shaft 25, so that all of the exhaust valves will be controlled coincidentally.

Suitable means are provided upon the end of the rock shaft 25, for effecting its described adjustment at the will of the operator, but such means are notshown here as their exact nature is immaterial.

The operation of the mechanism will be apparent. When the rock shaft 25 is in its starting position, as shown, all of the exhaust valves 4 of the engine will be slightly unseated so as to relieve the compression pressure in all of the engine cylinders. rotated for starting, with much less effort'than otherwise. Of course when the engine is being started the cam shaft i I will be caused to rotate and will actuate the valves as in the normal running of the engine, except that the exhaust valves,

when-they would otherwise be permitted to fully seat by their cams l3, will instead remain slightly open by engagement of the pins I8 with their compression release levers 20.

Once the engine has commenced firing, the rock shaft 25 is adjusted to lower the compression release levers 20, releasing the rollers H to exactly follow their cams l3, and permitting the exhaust valves to fully seat between their opening periods. ficiently long that, when the lever is in lowered or running position, the lever does not engage the pin l8, and the rocker is free to move wholly under the correlated influence of the valve springs and corresponding cam.

What I claim is:

1. In an engine having a spring-seated poppet valve and actuating gear therefor including a timed cam shaft having a cam thereupon, and a rocker interposed between said cam shaft and said valve, said rocker being mounted upon a shaft and having a cam follower part cooperating with said cam, compression release gear comprising a lever pivoted on said rocker shaft, said lever and said rocker having parts which cooperate with one another to thereby lift said rocker from said cam, and control means associated with said lever for adjusting the latter between a running position, wherein said rocker is free to follow said cam, whereby the valve will have timed actuation, and a starting position, wherein the rocker will be lifted from said cam, whereby Thus the engine crankshaft may be 7 The slot 22-of each lever 20 is sufrocker interposed between-said canr shaft-*and said valve, said rocker being-"mounted upon a shaft and carrying a pin -said pin having a'cam follower part and a part projectingtfnom-said rocker, compression release gear comprising -a lever pivoted on said rocker shaft, saidilever hav ing a part engageable with said 'projecting pin part for lifting said "follower from said campand control means associated with said-lever for-adijusting the latter between :a runnin'g position;

whereby the valve will have timed-actuation; and a starting position wherein the roller will be-liftl-i ed from said cam, whereby said-valve-willbe cracked open. a

3. In an engine having aspring-seatezdt popriet valve and actuating-gear. therefor including-a timed cam shaft'having acam thereupom. and a rocker mounted upon :a shaftand-= interposed between said cam shaft and said =va-lve,:--;saidrocker carrying a pin. having. a.,roller"cam-fo1s; lower mounted thereon and projecting from said rocker, compression release gear comprising a lever pivoted on said rocker shaft alongside :said rocker, said lever havinga part. engageable with the projecting part of said pin for :lifting-rsaid roller from said cam, andhaving fli'SlOttD clean 'said pin in the running operation of theuengine,

and control means associated withsaid-levenforadjusting the latter-between a running posh, tion wherein said roller is'free to. follow said cam and said pin is free to) move in said-slot, and a starting position wherein saidroller-"willbe lifted from said cam.

4. In an engine having aspring-seated Poppet valve and actuating. gear-therefor including-a timed cam shaft having a cam thereupomxanda rocker interposed between said ,carn shaft; and:

said valve, said rocker-being mountedulbll 1 said valve, said rocker ;-being mounted upon ai.

shaft and carrying a pin having a roller-cam,

follower mounted thereon, compression release gear comprising a lever pivoted on saidrocker,

shaft, said lever having a part en ageahle=,-with said pin for lifting said'roller from. saidcam, and control means associated with saidlevenfor adjusting the latter between a running position, wherein said roller. is free to .follow-"said'cam, and a starting position; wherein said.-roller-;will be lifted from said cam, said control 1118811860315. prising a rock shaft having a cam,-said-ro ck-shaft; being located beyondsaid cam shaft .with re lspect tosaid rocker shaft, and-said lever hav ing a cooperative extension beyond said pin and, which extension is engaged by-the.,cam,upon said last mentioned rock shaft,

HAROLD D. CHURCH wherein said roller is free to follow said: cam, 

